how can i make a low poly render on blender internal viewport render
As I mentioned before. Blender Render isn't my thing, but I think result is pretty close.

Materials:

I've used mostly default material. Just set Diffuse color and lower Specularity > Intensinity to 0.2.



Light:

Again, as simple as it can be.

Lamp set to Sun with Sky turned on. 
Shadow > Ray Shadow with Sampling > 5 and Soft Size > 5.



Note. Postion Light directly from top to bottom to have shadows right beneath objects.

World:

Under World tab set Horizontal an Zenith Color to some candy like colors.
Switch on Environment Lighthing and set it to Sky Color.



Blend file:

And here to play with.